Ringing control arrangement for two-way carrier telephone terminals



w. BRANDT 2,44795 RNG'NG',CONTROL4 RRNGEMENT FOR TWO WAY CARRER TELEPHONE TERMINAL Jam.. m 1947.

Filed April 50, 1945 L EEE md ill-ill LHU Ri di @m Rill mwi

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iNvENToR ix/aiiei Bmnd'j ATTORNEY Patented Jan. 28, 1947 RINGING CONTROL 'ARRANGEBIENT F0 TWO-WAY CARRIER TELEPHONE TER- c MINALS Walter Brandt, Jersey City, N. J., assignor to Federal Telephone Vand Radio Corporation, New7 York, N. Y., a corporation of Delaware Application April 30, 1945, Serial No. 591,068

10 Claims.

This invention relates to ringing control arrangements especially adapted for use in carrier current telephone systems.

A principal object is to provide an improved carrier communication system wherein the frequency or frequencies for control purposes, e. g. ringing control, is within the frequency range of the intelligence signal frequencies, and wherein an improved arrangement is provided for controlling the application of ringing current.

Another object is to provide a carrier signalling system with a two-way terminal having an improved ringing current generator and switching arrangement associated therewith which can be selectively controlled by low frequency ringing currents in one direction and by voice frequency ringing currents in the opposite direction.

A further object is to provide a voice frequency ringing current generator which in one set of signalling conditions acts as a highly selective amplifier discriminator, and as a ringing current generator of voice frequency in another set of conditions.

A feature of the invention relates to an improved two-way carrier telephone terminal for connecting a carrier frequency channel to a trunking line or switchboard, and employing a grid-controlled tube having circuit connections for causing it to act as a regenerative amplifier for controlling` the switching-in of a low frequency ringing current, and also responsive to a low frequency ringing signal from the trunk line to convert the amplifier into a ringing-out generator of voice frequency ringing current.

Another feature relates to an improved voice Y i frequency ringing current generator and intelligence signal discriminator, especially adapted for use in a two-way terminal between a carrier frequency channel and a voice frequency line.

A further feature relates to a discriminator for discriminating between voice frequency intelligence signals and voice frequency ringing signals, employing an electron tube with associated circuits whereby the operating characteristics of the tube can-be converted from a selective amplifler to a relatively high level voice frequency ringing current generator.

Other features and advantages not particularly set forth are nevertheless inherent in the arrangements forming the subject matter of the invention. Y l

Referring to the single gure of the drawing there is shown by way of example, one typical carrier frequency signalling system wherein the invention can be usefully embodied. It will be understood that in certain of its aspects the in? vention is not necessarily limited to voice frequency carrier communication systems, but is capable of applicationto similarsystems whereby discrimination can be effected between control function currents such as ringing currents and intelligence signals.

The drawing shows in somewhat generalized schematic form a two-branch two-way terminal which connects the low frequency or trunking line I to the carrier frequency channel 2. When a calling connection is to be extended from the line I to the line 2 a low frequency ringing current, e. g. 2O C. P. S., is applied over line I, thence through the armature 3 and associated back contact of relay 4, windings 5 and 6 of the hybrid coil arrangement 1, through low frequency condenser 8, armature 9 and associated back contact. Connected across condenser 8 in series with another condenser I0, is an alternating current relay II which operates in response to the 2() cycle ringing current, and at its armature I2 and associated front contact completes an operating circuit over conductor I3 through the winding of relay I4. Associated with relay I4 is a continuously operating carrier frequency generator tube I5 which may be of any well-known grid-controlled type. Merely for illustration it is shown as a pentode having its control grid coupled through the Oscillatory circuit I6, I1 in sustained feedback relation to a tuned oscillatory plate circuit comprising inductance I8 and parallel tuning condensers I9', 20, 2l for tuning the generator sharply tothe required carrier frequency.

The carrier generator is coupled through any suitable coupling transformer 22 to any wellknown modulatory device or network 23. Modulator 23 is arranged to have its input supplied with voice frequency signals representing either intelligence or ringing control, so that there is appliedV to the band-pass filter 24 a voice frequency modulated carried which is further amplified in a suitable carrier frequency amplifier 25,

and applied through the selective directional filter 25 to the carrier channel 2.

Also associated with relay I4 is a convertible amplier-to-cscillator tube 2l which, merely for illustration., is shown as of the pentode type. When relay I4 is deenergized the tube 2T acts as a highly selective amplifier having a slight amount of regeneration to increase its selectivity. For this purpose the control grid 28 is returned to the cathode 29 through winding 3l) of a voice frequency transformer 3| whose associated winding 32 is connected in the plate return circuit.

into the grid circuit under co-ntrol of relay i4. Each of V:the windings" 32, 34 is tuned by a reV spective condenser 35, 31 to the voice frequency used for ringing. In effect the elements 3l, 31 i constitute a sharply tuned ilter for the voicevv frequency ringing current ,Thus tube 2i does not operate as ringing current generator until a sufficient A. C. potential at the ringing frequency is applied to the grid 28.

When relay lll is operated in response to a ring-out signal from line I' as above described, the above-mentioned tuned feedback circuit is completed from plate 38 through armature 3S and its associated front contact, t grid 28. Tube Zi therefore generates a relatively high level ringing current of Voice frequency. This ringing frequency is applied over conductor d@ through the armature lil and associated front contact of relay id, conductor'lt, to the input terminals of low pass iilter 'e3 which is'coupled to modulator 23 through transformer dll. Thus there is ap plied to channel 2 a carrier signalV which is modulated by the ringing signal of voice frequency.

When it is desired to ring the trunk I from the line Z, there is received over the latter a similar carrier having a voice frequency ringing modulation'which passes through the high pass output terminals cf directional lter 25 and is applied to band-pass lter 115. Filter 45 is coupled through transformer le to a suitabledemodulator d1 which is supplied with carrier frequency oscillations from the oscillator tube 48 which may be similar to tube l5.` Therefore there exists at the coupling transformer t9. the demodulated signal representing the received ringing voice frequency. This voice frequency ringing signal is of relatively high level and is applied through low pass lter 55 and coupling transformer 5l to the re ceiving amplifier 52.

The output circuit of amplier 52 is coupled through condenser 53, over conductor d, armature 3S and associated back contact, to grid 23. In response to this voice frequency ringing signal applied to grid 28, tube 21 amplies it and the amplified signal is applied through armature il and its associated back contact of relay I4, thence through` rectifier 55 and a smoothing filter comprised of resistors 5E, 51 and condensers 58, 59. to the grid 28. The application of this additional l).V C. bias potential to grid v28 causes a proportionate increase in the D. C. plate current of tube 21 which flows through theY Winding of relay i to cause itto operate. When relay 4 operates, it i connects the cycle ringing current over co-nductors 6i) through the armatures 3 and 9 and their respective front contacts to the line l. During the transmission of intelligence signals, the hybrid coil 1 functions in the normal way to repeat the incoming intelligence from the output of the receiving amplifier- 52A through windings 5 and through the armatures and associated back contacts of relay l to the line l. During this period the voice frequency signals which reach the grid 28 through condenser 53 are of insuicient level at the ringing frequency to convert the tube 21 from an amplifier to an oscillator generator.

` While one particular embodiment has been disclosed herein, it Ywill be understood that various changes and modifications may. be. made therein 4 Without departing from the spirit and scope of the invention.

What is claimed is:

l. A two-way terminal of the character described comprising, a pair of branches for signalling in opposite directions, Va carrier oscillator, a device'effectivein one condition to act as an amplifier and in another condition to act as an `alternating current generatcn'means responsive to the application of a ringing signal to one end of said terminal to convert said device into a generator of alternating ringing current, and means for applying the generated currents to modulate the carrier from said oscillator and for applying the modulated carrier to the other end of said terminal.

2. A two-Way terminal of the character described comprising, a pair of branches for signalling in opposite directions, a carrier oscillator, a device effective in one condition to act as a selective amplifier and in another condition to frequency ringing-in current to said one end `of the terminal. Y

3. VA two-way carrier telephone terminal comv pricing, a transmitting branch and a receiving branch, means including a telephone line to apply a ringing control signal to one end of the terminal, means to apply a voice frequency ringing signal to the other end of the terminal, an amplifier which selectively amplies said voice frequency signal, means responsive to said amplification to produce a corresponding direct current component, and switching means responsive to said direct currentcomponent for disconnecting the said line from Said one end of the terminal and for applying a local ringing frequency to said line.

4. A tvvo-way terminal according to claim 3 Vin which said amplifier is provided with circuit are rangements for converting it into an alternating current generator of voice frequency ringing current under control of the application of said ringing control signal to saidone end of the terminal.

5. A two-Way carrier telephone terminal comprising a transmitting branch and a receiving branch, said transmitting branch having a carrier oscillator generator, a voicey frequency ringing generator of the feedback type Which is normally ineffective to generate ringing currents, means responsive to control signals applied to one end of said transmitting branch'to causesaid generator to generatavoice frequency ringing current under control of said feedback, and means to apply said voice frequency ringing currenttc modulate said carrier oscillator for impressing voice frequency modulated carrier on the other end of said transmitting branch.

6. A two-way carrier telephone terminal com# prising a transmitting branch, a receiving branch, said transmitting branch having an associated carrier current generator, an electronv tube-common to both branches and normally acting-as tube, a relay for switching-in said feedback arrangement to cause said tube to generate voice frequency ringing current, means responsive to a low frequency ringing signal for controlling said relay, and means to modulate the carrier generator of the transmitting branch by said voice frequency ringing signal.

7. A two-way carrier telephone terminal comprising a transmitting branch and a receiving branch, each branch having an associated carrier current generator, an electron tube common to both branches and normally acting as an amplifier, means in said receiving branch including said associated carrier current generator to deinodulate a received voice frequency ringing signal and applying it to the control grid of said electron tube whereby said voice frequency ringing signal is selectively amplified, means to rectify the amplified frequency signal in the plate current of said tube, mean-s to apply the rectified signal to the control grid of said tube to increase the D. C. plate current, vand a ringing control relay controlled by said increased D. C'. plate current.

8. In a carrier telephone voice frequency ringing control system, an electron tube, a feedback arrangement for causing said tube to generate voice frequency ringing current, a relay for switching said feedback arrangement into and out of circuit with said tube, a rectifier arrangement connected in the plate circuit of said tube under control of said relay, means controlled over a telephone line for operating said relay, means to apply the voice frequency ringing signals received over said receiving branch to the control grid of said tube to cause a marked increase in the current through said rectifier, and means to apply said low frequency ringing signal to a telephone line in response to said rectified current.

9. A voice frequency ringing current generatordiscriminator for carrier telephone terminals comprising an electron tube, a feedback arrangenient for said tube including a filter network sharply tuned to a voice frequency ringing signal, a rectifier arrangement connected between the plate and the control grid of said tube, a relay having contact-s effective in one position to conneet said rectifier arrangement in circuit with said grid and effective in another position to connect said feedback and filter in circuit, and means controlled over a telephone line for operating said relay.

10. A voice frequency ringing current generator-discriminator according to claim gl in which said tube has its control grid connected to a telephone receiving branch whereby demodulated voice frequency ringing signal is applied to said grid, a switching relay, and a D. C. plate return circuit for said tube connected through said switching relay for applying low frequency ringing signals to said telephone line.

WALTER BRANDT. 

